1. Field of the Invention
The present invention relates to a laser diode having a light detecting device and, more particularly, to a laser diode which can be suitably applied to uses requiring high-degree light detection precision.
2. Description of the Related Art
Hitherto, in a semiconductor light emitting device for a use with an optical fiber, an optical disk, and the like, a laser beam emitted from a laser diode is detected by a light-detecting mechanism as part of an object of making the light output level of the laser diode constant, which is assembled in the semiconductor light emitting device. The light detecting mechanism can include, for example, a reflector that branches part of a laser beam and a semiconductor photodetector that detects the branched laser beam. In the configuration, however, the number of parts increases and, moreover, an issue occurs such that the reflector and the semiconductor photodetector have to be disposed with high precision with respect to the laser diode. As one measure solving such an issue, the laser diode and the semiconductor photodetector are integrally formed.
However, when the laser diode and the semiconductor photodetector are formed integrally, there is the possibility that the semiconductor photodetector detects not only stimulated emission light to be detected but also spontaneous emission light. In such a case, the light output level of the laser diode measured on the basis of photocurrent obtained by conversion by the semiconductor photodetector includes an error only by the amount of spontaneous emission light. The spontaneous emission light changes according to temperature, operating current, and the like and makes the correlation between the laser beam and the photocurrent nonlinear. The method is also not suitable for uses requested to control the light output level with high precision.
Japanese Unexamined Patent Application Publication (Translation of PCT Application) (JP-T) No. 2003-522421 discloses a technique of providing one photodetection layer in a semiconductor photodetector in the position of an antinode of a standing wave in a laser beam to make stimulated emission light detected more easily than spontaneous emission light.